This no longer works on Froyo (EC05). Use Wifi Tether v3 instead after you root the phone. Beware, Wifi Tether sometimes is iffy and can really mess up your phone!
- Download one click root and root the phone
- Install Titanium backup from the market and remove Sprint hotspot
- Download MobileAP and put it on the sd card
- Download clockwork recovery
- Boot into clockwork recovery, apply the zip file from step 3
- Reboot the phone and goto Settings>Wireless and network>Mobile AP Settings to enable MobileAP